It's an all-too-common call to offices of the Florida Fish and
Wildlife Conservation Commission (FWC) this time of year."
There's a squirrel in my yard with lumps all over its body and it's
jumping in the air, rolling on the ground and acting crazy. What's wrong
with it," the typical caller asks.
Although squirrels might be acting a little, well, squirrelly this time of
year, biologists say it's really nothing to get alarmed about.
" When people call they describe these unusual antics, as well as
large lumps on the squirrel's body that appear to be cancerous
tumors," said Stan Kirkland, the FWC's public information coordinator
for the Northwest Region. "The good news is the lumps are not
malignant tumors. In fact, they are caused by 'warbles,' which are Bot
fly larvae growing just under the squirrel's skin." In fact, once the
larvae emerge in the fall, the squirrel generally recovers without further
incident. However, while the insects are burrowed under the skin,
they are a real annoyance to the squirrel. "In the Southeast United
States, gray squirrels and other
rodents, and rabbits, are commonly
affected by Bot fly warbles. Horses and cattle are sometimes
affected by them too," Kirkland said.
What happens is sometime during the summer months the female Bot fly,
which resembles a small bumble bee, deposits its eggs on tree limbs or
near the entrance to a squirrel's nest or den. The unsuspecting
squirrel or rabbit comes into contact with the eggs and enters the den to
sleep. Then when it grooms itself, its body heat and moisture causes
the eggs to hatch. The newly hatched larvae then penetrate the
squirrel through a body opening and migrate to a comfortable spot just
below the skin where they cut a breathing hole and continue their
development. Sometime during the fall the larvae will emerge from the
skin, drop to the ground and then pupate in the ground until next summer,
when they'll re-emerge as a fly and begin the process again.
"In gray squirrels, the larvae are most abundant in the late summer
and early fall. This is why people are seeing the lumps right
now," Kirkland said. "A few squirrels may become
debilitated if they are heavily infested, but most will suffer no
permanent effects from the parasite." In terms of health
issues, there is no threat to humans or pets from the larvae itself or the
affected animals. Most of the time squirrels that have warbles
recover fairly quickly in a matter of days.
Florida's small game season for squirrels comes later in the fall and
hunters rarely kill squirrels then that have Bot fly warbles. For
the time being, however, the best thing to do if you see these odd-acting
squirrels is to simply leave them alone and let nature take its course.
Eventually the problem will take care of itself and the squirrels will go
about the business of being squirrels.